The present disclosure relates to a flat panel display, a method of manufacturing an anode panel for the flat panel display, and a method of manufacturing a cathode panel for the flat panel display.
Various flat panel types of displays have been investigated as image displays to be replaced with cathode ray tubes (CRTs) which are currently mainstream. Typical examples of flat panel displays are liquid crystal displays (LCDs), electroluminescence displays (ELDs) and plasma displays (PDPs). Development of flat panel displays in which a cathode panel provided with electron emitters is also proceeding. Known examples of the electron emitters are cold cathode field emitters, metal/insulator/metal devices (also called MIM devices), and surface-conduction electron emitters, and flat panel displays of the type in which a cathode panel provided with electron emitters made of such a cold cathode electron source is incorporated are attracting attention from the viewpoints of color display of high resolution and high luminance and low power consumption.
A cold cathode field emission display (hereafter referred to also simply as the display) which is a flat panel display in which cold cathode field emitters are incorporated as its field emitters generally has a construction in which a cathode panel CP provided with a plurality of cold cathode field emitters (hereinafter referred to also simply as the field emitters) and an anode panel AP having phosphor areas which are excited to emit light by colliding with electrons emitted from the electron emitters are arranged in opposition to each other across a space maintained in high vacuum, and the cathode panel CP and the anode panel AP are joined together at their periphery by a joining member. The cathode panel CP has electron emission areas corresponding to individual subpixels arranged in a two-dimensional pixel, and each of the electron emission areas is provided with one or a plurality of field emitters. Typical examples of field emitters are Spindt types, flat types, edge types, plane types and the like.
FIG. 20 shows a schematic end view, in fragmentary cross section, of a display having Spindt field emitters by way of example, and FIG. 22 shows a schematic exploded view, in fragmentary perspective, of the cathode panel CP and the anode panel AP. Each of the Spindt electron emitters which constitutes the display includes a cathode electrode 11 formed on a support 10, an insulation layer 12 formed on the support 10 and the cathode electrode 11, a gate electrode 13 formed on the insulation layer 12, an opening section 14 provided to extend through the gate electrode 13 and the insulation layer 12 (a first opening section 14A provided in the gate electrode 13 and a second opening section 14B provided in the insulation layer 12), and a conical electron emission section 15 formed on the section of the cathode electrode 11 that is positioned at the bottom of the opening section 14.
FIG. 21 shows a schematic end view, in fragmentary cross section, of a display having so-called flat electron emitters each having an approximately flat electron emission section 15A. Each of the flat electron emitters includes the cathode electrode 11 formed on the support 10, the insulation layer 12 formed on the support 10 and the cathode electrode 11, the gate electrode 13 formed on the insulation layer 12, the opening section 14 provided to extend through the gate electrode 13 and the insulation layer 12 (the first opening section 14A provided in the gate electrode 13 and the second opening section 14B provided in the insulation layer 12), and an electron emission section 15A formed on the section of the cathode electrode 11 that is positioned at the bottom of the opening section 14. The electron emission section 15A is made of, for example, a multiplicity of carbon nanotubes partially embedded in the matrix.
An interlayer insulation layer 16 is provided over the insulation layer 12 and the gate electrode 13, and an opening section (a third opening section 14C) which communicates with the first opening section 14A provided in the gate electrode 13 is provided in the interlayer insulation layer 16, and a focusing electrode 317 is provided to extend from the top surface of the interlayer insulation layer 16 to the side walls of the third opening section 14C. In FIGS. 21 and 22, the illustration of the interlayer insulation layer and the focusing electrode is omitted.
In each of the displays, the cathode electrode 11 has a strip-like shape extending in a first direction (in each of FIGS. 20, 21 and 22, the X direction), while the gate electrode 13 has a strip-like shape extending in a second direction (in each of FIGS. 20, 21 and 22, the Y direction) different from the first direction (the X direction). In general, the cathode electrode 11 and the gate electrode 13 are respectively formed in the strip-like shapes in the directions in which projected images of the cathode and gate electrodes 11 and 13 are orthogonal to each other. An area in which one strip-shaped cathode electrode 11 and one strip-shaped gate electrode 13 overlap each other is an electron emission area EA, which corresponds to one subpixel. The electron emission areas EA are generally arranged in a two-dimensional matrix with an effective area of the cathode panel CP. The effective area is a central display area serving as a display function which is a practical function of the flat panel display, and an ineffective area is positioned outside the effective area and surrounds the effective area in a frame-like manner.
The anode panel AP has a structure in which phosphor areas 22 (specifically, red light emitting phosphor areas 22R, green light emitting phosphor areas 22G, and blue light emitting phosphor areas 22B) are formed on a substrate 20 in a predetermined pattern and the phosphor areas 22 are covered with an anode electrode 324. A light absorption layer (a black matrix) 23 made of a light absorption material such as carbon is formed between each of the phosphor areas 22 in order to prevent occurrence of color haze and optical crosstalk in display images. Each of the phosphor areas 22 which constitutes one subpixel is surrounded by a partition wall 21, and the planar shape of the partition wall 21 is a grate-like shape (a double-cross shape). In FIG. 20, reference numeral 40 denotes a spacer, reference numeral 25 denotes a spacer holding section, and reference numeral 26 denotes a joining member. In FIGS. 21 and 22, the illustration of the partition wall, the spacer and the spacer holding section is omitted.
One subpixel is made of one electron emission area EA provided on the cathode panel CP and one phosphor area 22 provided on the anode panel AP opposed to (facing) the electron emission area EA. In the effective area, such pixels are arranged on the order of, for example, several hundred thousand to several million. In a color display, one pixel is made of a set of a red light emitting subpixel, a green light emitting subpixel and a blue light emitting subpixel. During the fabrication of the display, the anode panel AP and the cathode panel CP are arranged so that the respective phosphor areas 22 are opposed to the electron emission areas EA, and the anode panel AP and the cathode panel CP are joined together at their periphery by the joining member 26 and the space therebetween is evacuated and sealed, thereby fabricating the display. The space surrounded by the anode panel AP, the cathode panel CP and the joining member 26 is held under high vacuum (for example, not higher than 1×10−3 Pa).
The presence of a foreign substance in the inside (space) of such a display is known as the cause of lowering the withstand voltage characteristics of the display to a significant extent. Measures against external foreign substances can be taken by means of manufacturing methods, manufacturing environments and the like all of which can prevent penetration of foreign substances into the display during the manufacturing process thereof.
However, in a heat treatment step of the manufacturing process of the display, there is a case where a kind of projection such as whiskers and/or hillocks is produced in the anode electrode 324 or the focusing electrode 317 made of aluminum. Incidentally, needle-shaped projections are called whiskers, and lump-shaped projections are called hillocks. Such projections in some cases become a cause of discharge when voltage is applied during the actual operation of the display. In addition, some of the projections are peeled by electrostatic force due to electric fields generated by voltage applied during the actual operation of the display, and become a foreign substance which is the cause of lowering the withstand voltage characteristics of the display to a significant extent.
It is believed that whiskers and hillocks are produced by compressive stresses due to the difference in thermal expansion between the anode electrode 324 or the focusing electrode 317 made of aluminum and the underlying base during a heat treatment step in the manufacturing process of the display. However, techniques for restraining the occurrence of whiskers and hillocks in the anode electrode 324 and the focusing electrode 317 have not yet been known.
For example, Japanese Patent Application Publication Number 2003-31150 discloses the technique of restraining generation of discharge by covering an anode electrode with oxide film or nitride film. However, this patent application publication does not include any description of the occurrence of whiskers and hillocks.